1. Field of the Invention
The present invention relates to a character processing apparatus which can output characters in designated sizes.
2. Related Background Art
Character processing apparatus have been developed which store character data in a ROM (read only memory) or an external storage device and outputs characters. In one such apparatus various kinds of characters in different character sizes to obtain outline effect, emphasis effect, and the like can be output to a display device, printer, or the like from a middle size to a large size with a data memory of a small capacity to output characters having a relatively high quality. In one practical embodiment of this character processing apparatus reference character data is stored as a coordinate point array on contours and the coordinate points are enlarged or reduced in accordance with the designated output size and thereafter, they are converted into dot information and output.
However, according to such a conventional apparatus, the reference character data is stored as absolute coordinate values of the coordinate points on contours and these coordinate values are merely multiplied by the enlargement rate or reduction rate according to the designated output size, thereby obtaining the final coordinates. Therefore, due to a digitization error which is caused when the coordinate values are made to correspond to the lattice points of the final output size, as shown in FIG. 4A, a variation occurs in horizontal or vertical line thicknesses, which should inherently be uniform. Particularly, when a character is converted into the character of a small size, there is a problem such that the apparent quality deteriorates remarkably.
On the other hand, in a character processing apparatus which has character data in an ROM or external storage device and outputs characters, there are many demands in recent years to output characters of a plurality of sizes in order to obtain an outline effect, an emphasis effect, or the like. To meet these demands, the following methods are used.
(1) All of the fundamental character data of the necessary sizes are stored as dot information in accordance with the resolutions of output devices (dot printer and the like). (For example, characters of 16.times.16 dots, 24.times.24 dots, 32.times.32 dots, etc.) PA1 (2) The fundamental dot information is variably magnified and output. PA1 (3) Character data is stored as a coordinate point array on contours. After this character data was enlarged or reduced in accordance with the designated output size, it is converted into the dot information and output. PA1 (4) The above methods (1) to (3) are combined and the like. PA1 a) According to the method of (1), the amount of character data is large. The cost is high. The character sizes which can be output are limited to the dot sizes of character data (e.g., 16.times.16, 24.times.24, 32.times.32, etc.). When character data is output by a printer of a high resolution, the dot size must be also enlarged in proportion to the high resolution. PA1 b) According to the method of (2), the quality of the enlarged or reduced output character remarkably deteriorates due to the variable magnification. The variable magnification range is also limited. PA1 c) According to the method of (3), although the drawbacks in the above items a) and b) can be eliminated, when character data is variably magnified (reduced) to output a character of a relatively small size, the ratio of error which is caused as the result of the arithmetic operation of the coordinate values increases. As shown in FIG. 4A, the thicknesses of horizontal or vertical lines, which should inherently be uniform, do not become uniform, so that the quality deteriorates. PA1 d) According to the method of (4), to eliminate the drawback of the above item c), dot data is output for a character of a small size and a character is output by the method of (3) for a character of a large size. However, the drawback in each method still remains.
However, the foregoing methods have the following problems in the conventional apparatuses.
Techniques regarding the outline font technique in which character data is stored as a coordinate point array on contour lines are disclosed in U.S. application Ser. No. 854,193 filed on Apr. 21, 1986, which issued as U.S. Pat. No. 4,817,172 on Mar. 28, 1989, U.S. application Ser. No. 596,737 filed on Aug. 22, 1990, now abandoned, and U.S. application Ser. No. 819,650 filed on Jan. 10, 1992, all of which have been assigned to the same assignee as this invention. Although these techniques are technically quite different from the present invention, they are concerned with the present invention with respect to a large concept of the outline font. According to those U.S. Patent disclosures, there are provided: the technique to independently thicken or thin in the vertical or lateral direction; the technique to uniformly thicken or thin; the technique for modification (shadow, hatching, or the like) of outline fonts; the technique to prevent the paint-out in the process to thin a contour or to realize notches of a generation pattern; and the like.
On the other hand, although the following techniques are also technically quite different from the present invention, U.S. Pat. No. Re. 30,679 has proposed techniques for variable magnification of outline fonts and for painting-out, and U.S. Pat. No. 4,408,198 (Kudirka) has proposed the technique to modify a pattern by the delay of every scan line in a video character generator, and the like.